Spinal derotation instruments and methods

ABSTRACT

Derotation instrument assemblies and systems are provided to facilitate positioning one or more vertebrae of a spinal column into a desired alignment. The instrument assemblies and systems include implant holders engageable to respective implants engaged to vertebrae of the spinal column, transverse bridges to connect implant holders associated with a particular vertebra, and inter-level linking assemblies to connect instrument assemblies associated with different vertebrae. Derotation handles can be provided to facilitate application of the alignment forces, while the assemblies distribute the corrective forces to the connected implants and vertebrae.

BACKGROUND

Surgical correction of the positioning and alignment of one or morevertebrae in the spinal column can be desired to address variouspathologies and conditions of patients. However, such repositioning andre-alignment can be time-consuming, cumbersome, and potentiallydifficult to achieve during a surgical procedure. For example, thealignment of multiple vertebral levels can require manipulation ofinstrumentation at each level to achieve the desired results. Forcesapplied to the vertebral body need to be controlled to minimize stresseson the vertebral bodies and implants. Furthermore, the alignment at onelevel should be maintained while other levels are aligned. In addition,the instrumentation employed to achieve the alignment can hinderplacement of stabilization constructs that post-operatively maintain thecorrected positioning and alignment achieved during surgery.

Therefore, instruments, methods and systems that facilitate surgicalcorrection of the alignment and positioning of a vertebra or vertebraeof the spinal column would be desirable. Furthermore, instruments,methods and systems that facilitate placement of stabilizationconstructs that post-operatively maintain the corrected vertebra orvertebrae are also desirable. In addition, instruments, methods andsystems that facilitate control of the stress exerted on implants andvertebrae to which the implants are attached would be desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a derotation instrument assembly coupledto implants engaged to a vertebra.

FIG. 2 is a perspective view of a derotation system for multiplevertebral levels.

FIG. 3 is an elevation view of an implant holder of the derotationinstrument assembly of FIG. 1 in a closed position.

FIG. 4 is an elevation view of the implant holder of FIG. 3 in an openposition.

FIG. 5 is an elevation view of the implant holder of FIG. 3 rotated 90degrees about its longitudinal axis.

FIG. 6 is a section view along line 6-6 of FIG. 5.

FIG. 7 is a perspective view of a first arm of the implant holder ofFIG. 3.

FIG. 8 is a perspective view of a second arm of the implant holder ofFIG. 3.

FIG. 9 is a sectional view looking proximally at a latch member of theimplant holder of FIG. 3.

FIG. 10 is a perspective view of a holding member of the implant holderof FIG. 3.

FIG. 11 is a perspective view of a release button of the implant holderof FIG. 3.

FIG. 12 is a perspective view of a transverse bridge with clampingassemblies of the derotation instrument assembly of FIG. 1.

FIG. 13 is a section view through line 13-13 of FIG. 12 and showing ahandle mount positioned about the link member of the transverse bridge.

FIG. 14 is a section view through line 14-14 of FIG. 13 with the linkmember removed from the handle mount.

FIG. 15 is an elevation view of a clamping assembly of FIG. 12.

FIG. 16 is a section view of the clamping assembly through line 16-16 ofFIG. 15.

FIG. 17A is a longitudinal section view of a derotation handle.

FIG. 17B is an elevation view of another embodiment derotation handleengaged to a transverse bridge.

FIG. 17C is a section view through line 17C-17C of FIG. 17B.

FIG. 18A is a perspective of another embodiment transverse bridge.

FIG. 18B is a perspective view looking toward the bottom of thetransverse bridge of FIG. 18A.

FIG. 19A is a perspective view of another embodiment transverse bridge.

FIG. 19B is a perspective view of another embodiment transverse bridgeand proximal portion of implant holders secured to one another with thetransverse bridge.

FIG. 20 is an elevation view of an inter-level linking assembly forlinking derotation instrument assemblies.

FIG. 21 is a section view through line 21-21 of FIG. 20 rotated 90degrees from its FIG. 20 orientation.

FIG. 22 is an elevation view of a handle extension engageable to animplant holder of FIG. 3.

FIG. 23 is a longitudinal section view of an outer handle member of thehandle extension of FIG. 22.

FIG. 24 is a longitudinal section view of an inner engaging member ofthe handle extension of FIG. 22.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended. Any such alterations and furthermodifications in the illustrated devices, and such further applicationsof the principles of the invention as illustrated herein arecontemplated as would normally occur to one skilled in the art to whichthe invention relates.

Spinal derotation instrumentation is provided to affect one or morederotation maneuvers on a scoliotic spine or on a spine having one ormore displaced, misaligned or curved vertebral levels. Specifically, aderotation instrument assembly is attached to at least one vertebralbody, with the assembly including at least one bone implant anchored tothe vertebral body along at least on of the left and right sides of thespinal column; an elongate implant holder removably attached to a headportion of the at least one bone implants. In embodiments employingmultiple implants engaged to a vertebral body, a transverse bridgeinterconnects the proximal end portions of the implant holders and aprimary handle extending axially from a central portion of thetransverse bridge in a direction generally parallel with the sagittalplane and implant holders for manipulation by the surgeon. One or morein-line de-rotation handles can be engaged to respective ones of theimplant holders to allow selective manipulation of an implant holder andimplant.

The derotation instrument assembly may also include a secondary handle,either along or in combination with the primary handle, extendinglaterally from an end portion of the transverse bridge (e.g., in adirection generally perpendicular or substantially transverse to theimplant holders and sagittal plane) for further manipulation by thesurgeon. The secondary handle may be threadingly or otherwise suitablyremovably engaged to the transverse bridge to allow for selectiveattachment and removal. In an alternative embodiment of the derotationinstrumentation, the transverse bridge may be eliminated, and amanipulation handle may be engaged directly to the proximal end of eachimplant holder, such as by threading engagement to allow for selectiveattachment and removal, for individual manipulation of the implantholders by the surgeon.

The bone implants can be configured as pedicle screws, with each screwhaving a head portion which includes a pair of arms defining a U-shapedchannel for receiving a spinal rod, and with the arms defining internalthreads for threadingly receiving a set screw for capturing the spinalrod within the U-shaped channel. The screw can be uni-axial, ormulti-axial so that the head can pivot relative to the bone engagingportion. In the illustrated embodiment, the head portions of the screwsare configured to receive stabilization element either through a topopening between the pair of arms or to receive an end of thestabilization element as it is passed through the head in an end-wisemanner. In another embodiment, the head portion of the screws opens to aside so that the stabilization element can be side-loaded therein. Otherembodiments contemplate any suitable type of implant that can be engagedto a vertebra and coupled to an elongated stabilization element.

The elongate implant holders can each include a distal end portionconfigured for selective clamping to either arm of the screw headportion. In one specific embodiment, the implant holder includes atubular body extending the length of the implant holder and a clampportion pivotally attached at the distal end portion of the tubular bodyvia a pivot pin. A spring may be included for biasing the clamp portiontoward an open position along with a releasable latching mechanism toreleasably capture the arm of the screw head portion between the distalend portions of the tubular body and the clamp portion. The implantholder may also include a release button to selectively release thetubular body and the clamp portion from the arm of the screw headportion. The implant holder can include a length so that at least itsproximal end is positioned outside the patient through the wound orincision in which the vertebrae are accessed.

The proximal end of the implant holder can include a threaded post thatis rotatably and pivotally coupled to the tubular body via a ball andsocket joint to allow for angular adjustment therebetween. The threadedpost of each implant holder is engaged to the transverse bridge via aclamping mechanism that is configured to slide along the length of anelongated connecting member at the transverse bridge. Such engagementbetween the implant holders and the transverse bridge allows forvariable lateral adjustment and variable angular adjustment of theimplant holders relative to the transverse bridge. The clampingassemblies can be provisionally tightened to the threaded post, and thenfinally tightened for secure engagement with a handle that serves as oneof the derotation handles.

In one embodiment, the transverse bridge is configured as a platedefining an elongate slot extending therethrough, with the threaded postof each implant holder positioned within the elongate slot and extendingthrough an aperture in a plate clamping assembly, which is in turnclamped onto opposite side portions of the plate via a knurled nut thatis tightened onto the threaded post. The primary handle may be removablyengaged to a central portion of the plate via a similarly-configuredhandle mount.

In another embodiment, the transverse bridge is configured as adiamond-shaped rod, with the threaded posts of each implant holderextending through an aperture in a rod clamping assembly, which is inturn clamped onto the diamond-shaped rod via a knurled nut tightenedonto the threaded post. The primary handle may be removably engaged to acentral portion of the diamond-shaped rod between the implant holdersvia a handle mount collar having a diamond-shaped aperture that can befixed about or slidably receives the diamond-shaped rod. The primaryhandle can be engaged to the handle mount collar.

Still other embodiments contemplate a transverse bridge having otherconfigurations. Such configurations include, but are not limited to,rack-and-pinion adjustment mechanisms, telescoping adjustmentmechanisms, and turn buckle adjustment mechanisms. In still anotherembodiment, the transverse bridge can connect implant holders engaged torespective ones of two or more vertebrae, and extend across the spinalmidline to link the implant holders to one another.

In instances requiring derotation across multiple vertebral levels, aderotation instrument assembly may be attached to respective ones of themultiple vertebral bodies requiring derotation, with the derotationinstrument assemblies being interconnected by an inter-level linkingassembly coupled between the individual derotation instrumentassemblies. As a result, the surgeon may manipulate an integrated frameassembly to affect derotation across multiple vertebral levels, ratherthan separately manipulating several derotation instrument assemblies toeffect derotation at each individual vertebral level. The transversebridge assembly can be releasably coupled to the implants holders suchthat the spacing and angular orientation between implant holders can bereadily adjusted and maintained with clamping assemblies that secure theimplant holders to a bridge member extending between the implantholders. The inter-level linking assemblies can be releasably coupled tothe primary handles, for example, such that the spacing and angularorientation between the primary handles and the linked derotationinstrument assemblies can be readily adjusted and maintained withconnector assemblies that secure the derotation instrument assemblies toan elongate link member extending between the derotation instrumentassemblies.

In one embodiment, the inter-level linking member is coupled between theprimary manipulation handles of the derotation instrument assemblies.However, the inter-level linking member may extend between otherstructures such as the clam ping assemblies that that connect theelongate implant holders to the transverse bridge or directly to thesecondary handles. In a specific embodiment, the inter-level linkingmember includes an elongate rod that is coupled to the primarymanipulation handles by a connector assembly that resembles a modifiedTSRH® 3D connector including a knurled nut for securing the connector tothe primary manipulation handle.

The inter-level linking assemblies can interconnect the derotationinstrument assemblies in a rigid fashion so that the engagementrelationship between the components is maintained during derotation ofthe spinal column. It is further contemplated that at least limitedslippage or movement between the inter-level linking assemblies and thederotation instrument assemblies can be provided as the spinal column isstraightened to accommodate non-uniform relative displacement among thecorrected vertebrae that may be required.

In FIG. 1 there is shown one embodiment of a derotation instrumentassembly 500 coupled to implants 550. Implants 550 are engaged to avertebral body Vl. In one specific application, implants 550 are boneanchors secured to respective ones of the pedicles of vertebral body Vl.Implants 550 each include a receiver portion 552 for receiving arespective elongated spinal stabilization element 554 positionable alongthe spinal column and securable to the implants to maintain apositioning of one or more vertebral bodies. In the illustratedembodiment, the implants are bone screws with a U-shaped head portionproviding a receiver to receive a spinal rod. Other embodimentscontemplate saddles, posts, clamping members, side-loading members orother receiver type members extending from a bone engaging portion inthe form of a staple, hook, screw, interbody device, intrabody device orother bone engaging member.

Derotation instrument assembly 500 includes implant holders 502removably engaged to respective ones of the implants 550 and extendingproximally therefrom. The implant holders 502 can be interconnected withone another in a bilateral fashion with a transverse bridge 504extending therebetween. Transverse bridge 504 includes a primaryderotation handle 506 extending therefrom at a location between implantholders 502. Primary derotation handle 506 extends in a direction thatis generally parallel to implant holders 502 and in a direction that isgenerally parallel to the sagittal plane of the spinal column. Asecondary derotation handle 508 can extend from transverse bridge 504 inthe same direction in which bridge 504 extends. Thus, secondaryderotation handle 508 can extend in a transverse orientation to implantholders 502 and in a direction that is generally parallel to the coronalplane of the spinal column.

Derotation instrument assembly 500 can be manipulated with one or bothof primary handle 506 and secondary handle 508 to displace, pull, twistor align the vertebra to which implants 550 is engaged into the desiredalignment with the spinal column. Accordingly, manipulation of multipleanchors engaged to the spinal column can be completed with asingle-handled approach, although the application of such forces throughmultiple handles is not precluded. For example, positioning of primaryhandle 506 in a medialized or central relation relative to the implants550 results in the corrective forces being distributed to both implantsand thus to multiple locations on the vertebral body. This can reducestress concentrations at any single bone/implant interface as themanipulation forces are applied.

It is further contemplated that a number of derotation instrumentassemblies 500 can be coupled to one another by one or more inter-levellinking assemblies 510 extending between and coupled to, for example,primary handles 506 and 506A of the respective assemblies 500 and 500Ashown in FIG. 2. The inter-level, linked instrument assemblies 500, 500Aprovide a derotation system 512 that facilitates the application of anddistribution of derotation, correction, alignment and other forces tovarious bony structures engaged by the bone implants and interconnectedwithin the system. Accordingly, the resultant stress on any one of theimplants and the bone to which the implant is engaged is distributed tomultiple locations and/or multiple vertebrae. It is contemplated thatany one, two or three or more vertebral levels with derotationinstrument assemblies 500 can be linked. It is further contemplated thatany subset of instrumented vertebral levels in a system could be linked.In addition or in lieu of linking primary handles 506, secondary handles508, transverse bridge 504, and/or implant holders 502 could be linked.

Referring now to FIGS. 3-11, one specific example of implant holder 502will be discussed with respect to an implant holder 10. Implant holder10 includes a first arm 12 in the form of a tubular body and a secondarm 14 providing a clamp portion pivotally coupled to first arm 12. Eachof the first and second arms 12, 14 includes a respective distal endportion 16, 18 of a distal holding end 20 of implant holder 10. Each ofthe portions 16, 18 forms a space in which to receive a portion of thebone implant, and further includes a projection 17, 19 extending intothe space toward the other portion 16, 18. The projections 17, 19 arereceived in detents formed in the receiver of the implant to whichholder 10 is engaged by clamping arms 12, 14 to the receiver of theimplant when implant holder 10 is closed, as shown FIG. 3 for example.To release the implant, implant holder 10 is opened by pivoting secondarm 14 about pivotal connection 22 with first arm 12, as shown in FIG.4.

Arms 12, 14 cross-over one another in a scissors type arrangement, andinclude inter-fitting recessed portions 30, 32, respectively, atconnection 22 so that end portions 16, 18 are aligned with one another.Furthermore, as shown in FIG. 5, arms 12, 14 include a slight bend sothat end portions 16, 18 are offset to one side of the longitudinal axis11 of implant holder 10. In addition, the space between end portions 16,18 opens away from axis 11 to so that the implant to which implantholder 10 is engaged can remain substantially unobstructed forengagement with another implant or system component.

Arms 12, 14 are spring biased toward the open position with a spring 24positioned in wells 26, 28 formed by respective ones of the arms 12, 14.Wells 26, 28 are oriented toward one another, and located proximally ofthe pivotal connection 22 between arms 12, 14. In order to secure arms12, 14 in the closed position in engagement with the implant, a latchingmechanism 40 is provided between arms 12, 14. Latching mechanism 40includes a latch member 42 extending from second arm 14 and a holdingmember 50 mounted to first arm 12 that is releasably engageable by latchmember 42. Latching mechanism 40 also includes a release button 70coupled to and extending proximally from holding member 50 between arms12, 14, and a spring 44 biasing holding member 50 into engagement withlatch member 42 and further biasing release button 70 proximally.

First arm 12 includes a collar 48 extending therefrom into a receptacledefined between arms 12, 14 in which latching mechanism 40 is locatedHolding member 50 extends through collar 48 and is axially movabletherein while collar 48 maintains holding member 50 in axial alignmentwith the remaining portions of latching mechanism 40. In addition, analignment pin 46 can be press fit in collar 48 and extend therefrom intoa slot 52 (FIG. 10) along a portion of the length of holding member 50to maintain holding member 50 in rotational alignment with latchingmechanism 40. Other embodiments contemplate that collar 48 and/oralignment pin 46 can be eliminated.

Holding member 50 is shown in further detail in FIG. 10. Holding member50 includes a central body 54 defining axial slot 52 therealong. Aconnector portion 56 extends from a proximal end of central body 54, andis threadingly received in a distal end opening of release button 70, asshown in FIG. 6. The distal end of central body 54 includes a radiallyoutwardly extending flange 58 that abuttingly engages collar 48 to limitthe proximal displacement of release button 70 and holding member 50under the bias of spring 44.

Holding member 50 also includes a stem 60 extending distally from flange58 to a latch receiving member 62. Latch receiving member 62 includes acylindrical body with inclined notched areas 64 and a central projectingarea 65 between inclined notched areas 64. In the open position, latchmember 42 includes sloped portions 43 that reside along inclined notchedareas 64, as shown in FIG. 8. When closing arms 12, 14 to engage theimplant between portions 16, 18, the sloped portions 43 slide along therespective adjacent inclined notched areas 64 to distally and axiallydisplace holding member 50 until the receptacle 45 (FIG. 9) of latchmember 42 aligns with and receives the cylindrical body of latchreceiving member 62, as shown in FIG. 6. In the closed position, arm 14is prevented from pivoting away from arm 12 by engagement of latchmember 42 around receiving member 62 of holding member 50. To releaselatch mechanism 40 and allow arm 14 to pivot away from arm 12, releasebutton 70 is depressed to displace holding member 50 distallysufficiently to align stem 60 with slotted opening 47 (FIG. 9) of latchmember 42. This allows receptacle 45 to become disengaged or displacedfrom about latch receiving member 62, and spring 44 pushes arm 14 awayfrom arm 12 and rotates arm 14 about connection 22 to the open positionof FIG. 4.

Release button 70 is further shown in FIG. 11, and includes a bodyportion 72 extending between a distal end member 74 and a proximal end76. Distal end member 74 defines the opening which receives connectorportion 56 of holding member 50. Proximal end 76 includes a concavelycurved surface to facilitate application of manual depression forceswith a thumb or finger to proximally displace button 70 and thus latchmechanism 40 between arms 12, 14. Button 70 is accessible through anotched area 13 of first arm 12, as shown in FIG. 5. An outwardlyextending lip 78 adjacent proximal end 76 can contact first arm 12 innotched area 13 to maintain alignment of release button 70 as it ismoved therein and to limit distal displacement of button 70.

Implant holder 10 further includes a proximal coupling mechanism 80.Coupling mechanism 80 includes a post 82 pivotal relative to first arm12, and captured thereon with an end cap 84. Coupling mechanism 80includes a base member 86 engaged to first arm 12 with a first pin 87.End cap 84 is coupled to base member 86 with a second pin 88. End cap 84defines a receptacle 90 in which a spring 92 is positioned. A washer 94is positioned against spring 92 opposite base member 86. Post 82includes a ball end 83 that rests against washer 94, and post portion 85extends through a proximal end opening 98 of end cap 84.

End opening 98 can be of any suitable shape and size to permit postportion 85 to extend therethrough. End opening 98 of end cap 84 caninclude a non-circular shape. For example, end opening 96 can be oval inshape such that in one direction relative to longitudinal axis 11, post82 can be pivoted up to an angle A, and in the transverse direction post82 can be pivoted up to angle B relative to longitudinal axis 11. In onespecific embodiment, angle A can range from 0 degrees to 15 degrees, andangle B can range from 0 degrees to 30 degrees. The convexly curvedshape at the proximal end of end cap 84 can receive components of thesystem, such as a clamping assembly 140, in any one of a number ofangular orientations relative to longitudinal axis 11. In addition, ballend 83 can rotate on washer 94 during such pivoting. Spring 92 biasesball end 83 of post 82 proximally against the inner wall surface of endcap 84. The inner wall surface can include a concavely curved shape thatextends around a portion of ball end 83 to facilitate rotation of ballend 83 thereagainst and thus the pivoting movement of post 82.

Post 82 can include opposite flat surfaces 89 extending therealong. Flatsurface can be provided so that components of the system being securedto post 82 are non-rotatable relative thereto during such engagement.For example, clamp assembly 140 can include a keyed bore portion 143(FIG. 16) that receives post 82 and flat surface 89 in form fittingengagement.

Referring now to FIGS. 12-16, one specific example of a transversebridge 504 is shown in the form of transverse bridge 100. Transversebridge 100 includes a transverse connecting member 102, a handle mount120 positioned about transverse connecting member 102, and a pair ofclamping assemblies 140 positioned about transverse connecting member102 on opposite sides of handle mount 120. Handle mount 120 can eitherbe fixed or slidable along connecting member 102, and clampingassemblies 140 can be slidably repositioned along transverse connectingmember 102. Clamping assemblies 140 can be clamped against transverseconnecting member 102 to maintain there respective positioningtherealong.

Transverse connecting member 102 can have a diamond shaped cross-sectionas shown in section view in FIG. 13. Other cross-sectional shapes arealso contemplated, including circular, square, rectangular, polygonal,and non-circular shapes, for example. Connecting member 102 extendsbetween a first end 103 and a second end 104. First end 103 can betapered as shown to facilitate placement of handle mount 120 andclamping assemblies 140 thereover. A non-tapered first end 103 is alsocontemplated. Second end 104 can include a connector portion 106 forconnection with a transverse secondary handle. In the illustratedembodiment, connector portion 106 is a threaded end member. Otherconfigurations for a connector portion 106 are also contemplated. Stillother embodiments contemplate that a connector portion 106 is notprovided. For example, a secondary handle can be provided that isintegrally formed with connecting member 102. In another embodiment, atransverse secondary handle can be clamped or otherwise secured directlyto the rod portion of connecting member 102 without a connector portion106 on connecting member 102. Still further, a transverse secondaryhandle connected to connecting member 102 can be omitted for one or moreof the transverse bridges of a derotation system.

Transverse connecting member 102 can further include first retainingmember 108 and second retaining member 110. Retaining members 108, 110can resist or prevent the handle mount 120, if slidable, and clampassemblies 140 from sliding off the end of connecting member 102 duringuse and manipulation of the surgical system. In one embodiment,retaining members 108, 110 are spring-biased ball-plunger typemechanisms that can be forced into respective holes in connecting member102 upon application of sufficient force to overcome the spring bias ofthe projecting ball member. However, the spring force is sufficient tomaintain the ball member projecting from the recess when contacted by aclamping assembly 140 or handle mount 120 sliding along connectingmember 102.

Handle mount 120 is shown in FIGS. 13-14, and includes a body portion122 and a connector portion 124 extending from body portion 122. Bodyportion 122 defines a passage 126 through which transverse connectingmember 102 extends. It is noted that connecting member 102 is removed inFIG. 14 for clarity in showing passage 126. Passage 126 can include across-sectional shape that mimics the shape of connecting member 102 toresist handle mount 120 from rotating about connecting member 102, andto facilitate the application of correction forces with a handle securedto handle mount 120. Handle mount 120 can be slidably positionable orfixed in position along connecting member 102.

Referring now to FIGS. 15-16, clamping assembly 140 is shown in furtherdetail. Clamping assembly 140 includes a clamping portion 142 and asecuring portion 144 that is operable to secure and release clampingportion 142 to transverse connecting member 102. Clamping portion 142includes a bore 146 for receiving proximal post 82 of the respectiveadjacent implant holder 10 discussed above. Bore 146 includes keyedportion 143 to non-rotatably receive post 82 in form fitting engagement.Clamping portion 142 further includes a passage 148 alignable withpassage 126 of handle mount 120 to receive connecting member 102 in atransverse orientation to implant holder 10. Passage 148 is defined byand between clamping arms 156, 158, which are movable toward one anotherto secure connecting member 102 therebetween. Specifically, clampingportion 142 includes a living or integral hinge 160 opposite arms 156,158 to facilitate such movement.

Securing portion 144 is rotatably retained and captured on a proximalend of clamping portion 142 with a retaining ring 150. Securing portion144 includes a threaded bore 152 that can threadingly engage theproximal post 82 of implant holder 10. In use, the distal end 154 ofclamping portion 142 is positioned in abutting engagement with the endcap 84 at the proximal end of implant holder 10 with post 82 extendingthrough bore 146 for engagement in bore 152 of securing portion 144. Assecuring portion 144 is rotated and threaded distally along post 82 ofimplant holder 10, arms 156, 158 move about hinge 160 since clampingportion 142 is pressed between the proximal end cap 84 of implant holder10 and securing portion 144. Securing portion 144 can be threadedproximally along post 82 to loosen or unclamp clamping portion 142 fromconnecting member 102 and allow repositioning of clamping assembly 140along connecting member 102.

Referring now to FIG. 17A, a longitudinal section view of one embodimentfor the primary and secondary derotation handles 506, 508 is shown inthe form of derotation handle 300. Primary handle 300 includes anelongate hollow cylindrical-type shaft 302 extending between a proximalend 304 and a distal end 306. A coupling portion 308 is providedadjacent distal end 306, and includes an internally threaded profile toengage connector portion 124 of handle mount 120. Other couplingarrangements between derotator handle 300 and handle mount 120 ortransverse connecting member 102 are also contemplated, includingnon-threaded coupling arrangement, snap fits, interference fits,supplemental connectors such as a set screw, clamping arrangements,bayonet locks, and integral connections, for example. Coupling portion308 can further include a distal socket 309 to allow handles 506, 508 tobe employed as a tool during the surgical procedure. For example, socket309 can be employed to tighten clamping assemblies 140 to connectingmember 102 by positioning the socket portion 309 over a nut comprising aportion of securing portion 144.

In FIGS. 17B-17C, another embodiment primary derotation handle 350 isshown coupled to connecting member 102 of transverse bridge 100. Handle350 includes an elongate shaft 354 rotatably coupled to a distalclamping mount 352. Clamping mount 352 is positioned about and slidablealong connecting member 102. Shaft 354 of handle 350 can be rotated forselectively loosening handle 350 for movement along connecting member102 and then tightened by rotating shaft 354 to secure handle 350 inposition along connecting member 102.

Clamping mount 352 includes a receiving member 358 for slidablyreceiving connecting element 102 through a passage 360 in a distalportion of receiving member 358. Receiving member 358 includes aproximal stem 362 coupled to shaft 354 with a coupling portion 364.Coupling portion 364 is secured to the distal end of shaft 354 andincludes an internally threaded bore for threadingly engaging stem 362.A clamping member 366 extends about and is axially retained on couplingportion 364 such that shaft 354 and coupling portion 364 can be rotatedwithout rotating clamping member 366. Furthermore, clamping member 366extends outwardly from proximal stem 362 so clamping member 366 isadjacent to and in contactable with connecting member 102.

In use, clamping member 366 and receiving member 358 can be moved towardone another by threadingly advancing coupling portion 364 and shaft 354along stem 362, forcing clamping member 366 against connecting member102 and securing connecting member 102 in clamping engagement betweenclamping member 366 and receiving member 358. Handle 350 can be quicklyreleased by rotating shaft 354 to unclamp connecting member 102 frombetween clamping member 366 and receiving member 358 when it is desiredto reposition handle 350 along connecting member 102.

Other embodiment transverse bridge, implant holders, derotationinstrument assemblies and systems are also contemplated. For example,FIGS. 18A and 18B show a transverse bridge 1100 having a transverseconnecting member in the form of a plate 1102. Plate 1102 is elongateand includes a central slot 1104 and side members 1106 extendingtherealong. The ends of the side members 1106 are connected by endmembers 1108. A connector portion 1110 extends from one of the endmembers 1108 for connection with a secondary derotation handle.

Transverse bridge 1100 includes a handle mount 1120 and clamp assemblies1140 movable along and securable to plate 1102. Handle mount 1120 andclamp assemblies 1140 can be similar to those discussed above withrespect to transverse bridge 100, but include oppositely extendingclamping portions to clampingly engage each of the side members 1106 ofplate 1102. For example, handle mount 1120 includes a body portion 1122having an upper clamp half 1125 and a lower clamp half 1123 positionableon opposites sides of the side members 1106. A connector portion 1126extends from lower clamp half 1123, and includes upper clamp half 1125axially movable and axially retained thereabout. The derotation handle300 can be secured to connector portion 1126 and into contact with upperclamp half 1125 to securely clamp plate 1102 between clamp halves 1123,1125.

Similarly, clamping assemblies 1140 can include a clamping portion 1142having an upper clamp half 1145 and a lower clamp half 1143. A securingportion 1144 extends through clamping portion 1142 and axially retainsthe clamping halves 1143, 1145 thereabout. Securing portion 1144includes a bore 1146 with flats 1147 to non-rotatably receive post 82therein. Securing portion 1144 is further rotatable within clampingportion 1142 to threadingly engage post 82 of implant holder 10. Assecuring portion 1144 is tightened onto implant holder 10, securingportion 1144 compresses clamping halves 1143, 1145 against the proximalend of implant holder 10 and thus toward one another for securement toside members 1106 of plate 1102.

A transverse bridge 2100 having a transverse connecting member in theform of a threaded transverse connecting rod 2102 having a length sizedto extend between and be secured to implant holders is shown in FIG.19A. A handle mount 2120 includes a body portion 2122 in the form of asleeve positioned about and threadingly engaged to connecting member2102. A connecting portion 2124 extends from body portion 2122 and isconfigured to receive a derotation handle thereover. In one embodiment,connecting portion 2124 can receive a quick connect type handle for easeof assembly. The positioning of handle mount 2120 along connectingmember 2102 can be adjusted if desired by rotating body portion 2122about connecting member 2102.

Transverse bridge 2100 further includes clamping assemblies 2140 at theends of connecting member 2102 on opposite sides of handle mount 2120.Clamping assemblies 2140 each include a clamping portion 2142 thatincludes a sleeve 2144 positionable about implant holder 10, and asplit-ring type clamping member 2146 that is moveable to release andsecurely engage sleeve 2144. Clamping member 2146 includes ends 2148,2149 engaged to connecting member 2102. Ends 2148, 2149 are movabletoward and away from one another by threading a respective clamping nut2150 along connecting member 2102. The clamping nuts 2150 can compressends 2148, 2149 together, which in turn tightly grips clamping member2146 about sleeve 2144. Sleeve 2144 can be provided with aconcave-convex interface with clamping member 2146 to provide angularadjustability between the implant holder and the clamping member 2146.In another embodiment, clamping member 2146 is clamped directly about aball member, post, or other portion of the implant holder without sleeve2144.

In the illustrated embodiment, one of the clamping members 2146 is fixedin position along connecting member 2102, while the other can beadjusted in position along connecting member 2102 by relocating anadjusting nut 2152 along connecting member 2102. Other embodimentscontemplate that the positioning of both of clamping members 2146 can beadjustable along connecting member 2102.

FIG. 19B shows another embodiment transverse bridge 3100 having aconnecting member in the form of a rack and pinion mechanism 3102extending between implant holders 10. Rack and pinion mechanism 3102 canbe engaged to the implant holders with clamping assemblies at the endsof the rack and pinion mechanism 3102. In one embodiment, rack andpinion mechanism can be the same or similar to that disclosed in U.S.Patent Application Publication No. 2003/0167059, which is incorporatedherein by reference.

Referring now to FIGS. 20-21, there is shown one embodiment of theinter-level linking assembly 510 in the form of inter-level linkingassembly 200 having a link member 202 and connector assemblies 220.Inter-level linking assembly 200 is positionable to extend between andbe coupled to portions of the system engaged to a vertebra or vertebraeof the vertebral level or vertebral levels to be aligned. For example,one or more connector assemblies 220 can be engaged to the respectiveprimary handles, clamping assemblies, or the transverse handles. Linkingof the one or more vertebral levels with inter-level linking assembly200 allows corrective forces to distribute to multiple vertebral bodiesand implants when applied with the primary or secondary derotationhandles. Connector assemblies 220 can be moved along the length of linkmember 202 and secured at various positions therealong to accommodatethe spacing between the components to be secured to inter-level linkingassembly 200.

Link member 202 includes a rod or shaft-like body 204 extending betweenopposite ends 206, 208. Ends 206, 208 can include an enlarged,flange-like projection to prevent connector assemblies 220 from slidingoff the ends thereof. Body 204 can include a circular cross-section asshown, or any other cross-sectional shape.

Connector assemblies 220 include a connector 222 having a passage 224for receiving an element to which inter-level linking assembly 200 is tobe connected, such as primary handle 300 as shown in FIG. 2. Connector222 is coupled to a receiving member 226 with a clip 230 in a bore 232at one end of receiving member 226. Clip 230 includes ears that extendinto bore 232 and can deflect toward one another to facilitate assemblyof connector 222. Furthermore, clip 230 is configured relative to bore232 so that connector 222 can be rotated within bore 232. Receivingmember 226 includes a central passage 228 through which link member 202extends. The other end of receiving member 226 includes an extension 234for threadingly receiving a clamping nut 236. A pin 238 in clamping nut236 contacts the threads on extension 234 to prevent clamping nut 236from being inadvertently removed.

Connector assembly 220 further includes a pair of clamping members 240,242 that are moveable toward and away from one another to secure andrelease link member 202 therebetween. A washer 244 can be providedbetween clamping nut 236 and the first clamping member 240 to facilitatetransfer of axial forces as clamping nut 236 is rotated.

A connector washer 246 is provided between second clamping member 242and passage 224 of connector 222. A spring washer 250 or other suitablespring member between second clamping member 242 and connector washer246 can bias clamping member 242 and connector washer 246 away from oneanother. Clamping nut 236 can be rotated along extension 234 to secureclamping members 240, 242 in clamping engagement on opposite sides oflink member 202, securing connector assembly 220 in position along linkmember 202. In addition, the system element in passage 224 is pressedagainst connector washer 246, securing the element between connector 222and connector washer 246.

A serrated, splined surface interface can be provided between secondclamping member 242 and connector washer 246 to provide a lockingarrangement therebetween when the element is engaged in passage 224.Spring 250 normally biases the serrated surfaces away from one anotherso that the surfaces do not contact one another and interfere withadjusting the orientation of connector 222 and connector washer 246relative to clamping member 242 and link member 204. Clamping members240, 242 can each include a recessed surface 241, 243, respectively, toreceive link member 202 therein in nesting or substantially nestingengagement. In addition, connector washer 246 can include a recessedsurface 247 to nestingly or substantially nestingly receive the portionof the element extending through passage 224 of connector 222.

It may further be desirable to provide a handle extension extendingproximally from one or more of the implant holders 10 for selectivemanipulation of an implant holder 10 and the vertebra to which it isattached. In FIGS. 22-24 there is shown handle extension 400 comprisingan outer handle member 402 and an inner engaging member 404. Outerhandle member 402 includes an elongate, sleeve-like body 406 extendingbetween a distal end 408 and a proximal end 410. Distal end 408 includesa distal opening 412 shaped like the proximal end cap of implant holder10 for receipt thereof in form-fitting engagement. There is furtherprovided a bore 414 through which the post 82 of implant holder 10extends. Bore 414 extends between and opens in distal opening 412 and acentral bore 416. Bore 414 can also be keyed like bore portion 143discussed above to receive post 182 in form fitting and non-rotatableengagement.

Engaging member 404 includes a shaft like body 420 extending between aproximal handle end 422 and a distal bore 424. Body 420 can extendthrough outer handle member 402 with proximal handle end 422 extendingproximally therefrom for access and grasping by the surgeon orattendant. Distal bore 424 is positioned proximally of bore 414 forengagement with the post 82 of implant holder 10. Bore 414 can be keyedto post 82 in form fitting engagement with flat surfaces 89 to preventrotation of post 82 in bore 414. Engaging member 404 is axially retainedbut rotatable within outer handle member 402 with a retaining member 426positioned between circumferential groove 418 formed in outer handlemember 402 adjacent proximal end 410 thereof and circumferential groove428 about engaging member 404 at the distal end of handle end 422.

In use, distal opening 412 is positioned about post 82 so that itextends through bore 414. Distal opening 412 has a distal cylindricalportion 413 that receives end cap 84 in a uni-axial manner so thathandle extension 400 extends along the axis of implant holder 10 whenengaged thereto. Handle extension 400 can be threadingly engaged to post82 by rotating engaging member 404 and threading it along post 82.Handle extension 400 can be advanced along post 82 to seat end cap 84 indistal opening 412. Handle extension 400 is fixed to implant holder 10,and can be manipulated to apply corrective forces through implant holder10 and the implant engaged to the vertebra.

In another embodiment, distal opening 412 does not include a cylindricalportion 413, but that has a spherical portion that opens directly at thedistal end of handle extension 400. Post 82 can be adjusted to thedesired angle relative to the remaining portion of implant holder 10.Handle extension 400 can then seated with its spherical end opening onthe spherical end of end cap 84 in any one of a number of axialorientations relative to the axis of implant holder 10 and engaged inany one of such orientations by threaded engagement with post 82.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character. All changes andmodifications that come within the spirit of the invention are desiredto be protected.

1. A system for correcting alignment of one or more vertebrae of aspine, comprising: first and second implants engageable to one of theone or more vertebrae, said first and second implants being configuredfor engagement with respective ones of first and second stabilizationelements positionable along the spine; and a derotation instrumentassembly including first and second elongated implant holders releasablyengaged to respective ones of said first and second implants, atransverse bridge positionable between and directly engaged to each ofthe first and second implant holders at a location spaced proximallyfrom said first and second implants, and a primary derotation handleextending from said transverse bridge on a line directly between saidfirst and second implant holders and orientable in a direction extendinggenerally parallel to a sagittal plane of the spine, said primaryderotation handle being associated with said bridge in a manner thatpermits forces applied to said handle to be directed to said transversebridge, thereby manipulating said first and second implant holders atsaid location wherein said transverse bridge is engaged thereto andcausing said first and second implant holders to manipulate said firstand second implants when engaged to said first and second implantholders.
 2. A system for correcting alignment of one or more vertebraeof a spine, comprising: first and second implants engageable to one ofthe one or more vertebrae, said first and second implants beingconfigured for engagement with respective ones of first and secondstabilization elements positionable along the spine; and a derotationinstrument assembly including first and second elongated implant holdersreleasably engaged to respective ones of said first and second implants,a transverse bridge positionable between and directly engaged to each ofthe first and second implant holders at a location spaced proximallyfrom said first and second implants, and a primary derotation handleextending from said transverse bridge at a location between said firstand second implant holders and orientable in a direction extendinggenerally parallel to a sagittal plane of the spine, said primaryderotation handle being associated with said bridge in a manner thatpermits forces applied to said handle to be directed to said transversebridge, thereby manipulating said first and second implant holders atsaid location wherein said transverse bridge is engaged thereto andcausing said first and second implant holders to manipulate said firstand second implants when engaged to said first and second implantholders, further comprising a secondary handle extending from an end ofsaid transverse bridge in a direction substantially transverselyoriented to said first and second implant holders and said primaryderotation handle.
 3. The system of claim 1, further comprising a secondderotation instrument assembly including third and fourth elongatedimplant holders releasably engageable to respective ones of the thirdand fourth implants engageable to a second one of the one or morevertebrae, a second transverse bridge positionable between andengageable to each of the third and fourth implant holders at a locationspaced proximally from said third and fourth implants, and a secondprimary derotation handle extending from said second transverse bridgeat a location between said third and fourth implant holders andorientable in a direction extending generally parallel to the sagittalplane.
 4. The system of claim 3, further comprising an inter-levellinking assembly extending between and engaged to each of said primaryderotation handles.
 5. A system for correcting alignment of one or morevertebrae of a spine, comprising: first and second implants engageableto one of the one or more vertebrae, said first and second implantsbeing configured for engagement with respective ones of first and secondstabilization elements positionable along the spine; a derotationinstrument assembly including first and second elongated implant holdersreleasably engaged to respective ones of said first and second implants,a transverse bridge positionable between and directly engaged to each ofthe first and second implant holders at a location spaced proximallyfrom said first and second implants, and a primary derotation handleextending from said transverse bridge at a location between said firstand second implant holders and orientable in a direction extendinggenerally parallel to a sagittal plane of the spine, said primaryderotation handle being associated with said bridge in a manner thatpermits forces applied to said handle to be directed to said transversebridge, thereby manipulating said first and second implant holders atsaid location wherein said transverse bridge is engaged thereto andcausing said first and second implant holders to manipulate said firstand second implants when engaged to said first and second implantholders; a second derotation instrument assembly including third andfourth elongated implant holders releasable engageable to respectiveones of the third and fourth implants engageable to a second one of theone or more vertebrae, a second transverse bridge positionable betweenand engageable to each of the third and fourth implant holders at alocation spaced proximally from said third and fourth implants, and asecond primary derotation handle extending from said second transversebridge at a location between said third and fourth implant holders andorientable in a direction extending generally parallel to the sagittalplane; and an inter-level linking assembly extending between and engagedto each of said primary derotation handles, wherein said inter-levellinking assembly includes an elongate link member extending between saidprimary derotation handles and connector assemblies movable along saidlink member and engageable to respective ones of said primary derotationhandles to connect said primary derotation handles to said link member.6. The system of claim 5, wherein said connector assemblies include: aconnector defining a passage for receiving said respective primaryderotation handles; a receiving member extending from said connector,said receiving member including a bore for receiving said link membertherethrough in a transverse orientation to said primary derotationhandles; a pair of clamping members about said receiving member onopposing first and second sides of said link member; a connector washerabout said receiving member between said passage and said clampingmember on said first side of said link member; and a clamping nutthreadingly engageable along said receiving member on said second sideof said link member with the other of said pair of clamping membersbetween said clamping nut and said link member, said clamping nut beingselectively operable to clamp said link member between said clampingmembers and said primary derotation handle between connector and saidconnector washer.
 7. A system for correcting alignment of one or morevertebrae of a spine, comprising: first and second implants engageableto one of the one or more vertebrae, said first and second implantsbeing configured for engagement with respective ones of first and secondstabilization elements positionable along the spine; and a derotationinstrument assembly including first and second elongated implant holdersreleasably engaged to respective ones of said first and second implants,a transverse bridge positionable between and directly engaged to each ofthe first and second implant holders at a location spaced proximallyfrom said first and second implants, and a primary derotation handleextending from said transverse bridge at a location between said firstand second implant holders and orientable in a direction extendinggenerally parallel to a sagittal plane of the spine, said primaryderotation handle being associated with said bridge in a manner thatpermits forces applied to said handle to be directed to said transversebridge, thereby manipulating said first and second implant holders atsaid location wherein said transverse bridge is engaged thereto andcausing said first and second implant holders to manipulate said firstand second implants when engaged to said first and second implantholders, wherein said transverse bridge includes: an elongatedconnecting member positionable between said implant holders; first andsecond clamping assemblies extending between said connecting member andrespective ones of said first and second implant holders to couple saidconnecting member to said respective implant holder; and a handle mountengaged to said connecting member between said first and second clampingassemblies, said primary derotation handle extending from said handlemount.
 8. The system of claim 7, wherein said primary handle isremovably coupled to said handle mount.
 9. The system of claim 7,wherein said handle mount is movable along said connecting memberbetween said clamp assemblies.
 10. The system of claim 7, wherein saidfirst and second clamping assemblies each include: a clamping portionincluding a bore for receiving a proximal post extending from saidrespective implant holder, said clamping portion further including apair of arms extending therefrom for receiving said connecting membertherebetween; and a securing portion rotatably mounted to a proximal endof said clamping portion and removably engageable to said post of saidrespective implant holder, wherein said securing portion is operable tomove said pair of arms toward one another to engage said connectingmember between said pair of arms as said securing member is engaged tosaid proximal post thereby clamping said clamping portion between saidsecuring member and said respective implant holder.
 11. The system ofclaim 10, wherein clamping portion includes a hinge portion oppositesaid pair of arms and said pair of arms are movable about said hingeportion.
 12. The system of claim 7, wherein said connecting memberincludes an elongated plate positionable between said implant holdersand having at least one opening therethrough.
 13. The system of claim12, wherein said at least one opening includes an elongated slot withside members extending along said slot and end members extending betweensaid side members and said handle mount and said clamping assemblies aremounted in said slot.
 14. The system of claim 7, wherein said connectingmember includes an elongated threaded rod positionable between saidimplant holders.
 15. The system of claim 7, wherein said connectingmember includes a rack and pinion mechanism positionable between saidimplant holders.
 16. The system of claim 7, wherein said connectingmember includes a non-circular cross-section along a substantial portionof a length thereof.
 17. A system for correcting alignment of one ormore vertebrae of a spine, comprising: first and second implantsengageable to one of the one or more vertebrae, said first and secondimplants being configured for engagement with respective ones of firstand second stabilization elements positionable along the spine; aderotation instrument assembly including first and second elongatedimplant holders releasably engageable to respective ones of said firstand second implants, wherein at least one of said implant holdersincludes a first arm and a second arm extending along a longitudinalaxis, said first and second arms each being pivotally connected to oneanother with distal portions thereof offset to a first side of saidlongitudinal axis and movable between a closed position in clampingengagement with a respective one of said first and second implants andan open position for releasing said respective implant, said derotationinstrument assembly further including a transverse bridge positionablebetween and engageable to each of said first and second implant holdersat a location spaced proximally from said first and second implants andproximally of said pivotal connection of said arms of said at least oneimplant holder; and a derotation handle engaged to said transversebridge.
 18. The system of claim 17, wherein said derotation handleextends from said transverse bridge at a location between said first andsecond implant holders and in a direction extending generally parallelto a sagittal plane of the spine and said first and second implantholders.
 19. The system of claim 17, wherein said distal end portionsfurther define an opening along one side thereof oriented away from saidlongitudinal axis.
 20. The system of claim 19, wherein said distal endportions are movable toward one another to grip said implanttherebetween by pivoting a proximal end of said second arm toward saidfirst arm.
 21. The system of claim 20, wherein said distal end portionseach include a projection extending toward the other of said distal endportions, said projection being received in detents in said implant whensaid implant holder is in a closed position.
 22. The system of claim 17,wherein said at least one implant holder includes a latching mechanismfor locking said first and second arms in said closed position.
 23. Thesystem of claim 17, wherein said first and second arms are spring biasedtoward said open position.
 24. The system of claim 17, wherein saidfirst arm includes a length along said longitudinal axis that is greaterthan a length of said second arm along said longitudinal axis, whereinsaid first arm includes a post extending proximally from a proximal endthereof for engagement with a portion of said transverse bridge.
 25. Thesystem of claim 24, wherein said first arm includes an end cap at saidproximal end thereof, said end cap defining a receptacle and said postincluding a ball end pivotally captured in said receptacle, said postfurther including a post portion extending proximally through said endcap in pivotal relation to said first arm of said implant holder. 26.The system of claim 25, wherein said portion of said transverse bridgeincludes a clamping assembly, said clamping assembly including: aclamping portion including a bore for receiving said proximal postextending from said at least one implant holder, said clamping portionfurther including a pair of arms extending therefrom for receiving aconnecting member of said transverse bridge therebetween; and a securingportion rotatably mounted to a proximal end of said clamping portion andremovably engageable to said post of said at least one implant holder,wherein said securing portion is operable to move said pair of armstoward one another to engage said connecting member between said pair ofarms as said securing member is engaged to said proximal post therebyclamping said clamping portion between said securing member and said endcap of said at least one implant holder.
 27. The system of claim 26,wherein clamping portion includes a hinge portion opposite said pair ofarms and said pair of arms are movable about said hinge portion.
 28. Asystem for correcting alignment of one or more vertebrae of a spine,comprising: first and second implants engageable to respective first andsecond vertebrae, said first and second implants being configured forengagement with a stabilization element positionable along the spine; afirst derotation instrument assembly including a first implant holderreleasably engageable to said first implant, a first transverse bridgedirectly engaged to a proximal end of said first implant holder, saidfirst transverse bridge extending from said first implant holder toanother implant holder for engagement with the another implant holder; asecond derotation instrument assembly including a second implant holderreleasably engageable to said second implant, a second transverse bridgedirectly engaged to a proximal end of said second implant holder, saidsecond transverse bridge extending from said second implant holder toanother implant holder for engagement with the another implant holder;and an inter-level linking assembly coupled to said first and secondtransverse bridges at a location between said implant holders of each ofsaid first and second derotation instrument assemblies.
 29. The systemof claim 28, wherein each of said implant holders includes a pivotalpost extending proximally therefrom and said first and second transversebridges are coupled with said pivotal post of said respective first andsecond implant holders.
 30. The system of claim 28, further comprising:a first primary derotation handle extending from said first transversebridge at a location spaced from said first implant holder, said firstprimary handle extending generally parallel to a sagittal plane of thespine; a second primary derotation handle extending from said secondtransverse bridge at a location spaced from said second implant holder,said second primary handle extending generally parallel to the sagittalplane; and said inter-level linking assembly includes first and secondconnecting assemblies coupled to respective ones of said first andsecond primary derotation handles, said inter-level linking assemblyfurther including a link member extending between and engaged to saidconnecting assemblies.
 31. The system of claim 30, wherein at least oneof said first and second connecting assemblies is movable along saidlink member and securable to said link member at any one of a number ofpositions therealong to adjust a spacing between said connectingassemblies.
 32. The system of claim 30, wherein said connectorassemblies include: a connector defining a passage for receiving saidrespective primary derotation handles; a receiving member extending fromsaid connector, said receiving member including a bore for receivingsaid link member therethrough in a transverse orientation to saidprimary derotation handles; a pair of clamping members about saidreceiving member on opposing first and second sides of said link member;a connector washer about said receiving member between said passage andsaid clamping member on said first side of said link member; and aclamping nut threadingly engageable along said receiving member on saidsecond side of said link member with the other of said pair of clampingmembers between said clamping nut and said link member, said clampingnut being selectively operable to clamp said link member between saidclamping members and said primary derotation handle between connectorand said connector washer.